In the art of recovering waste materials and, more particularly, mixed waste materials as well as industrial processing trim, rejects, scrap, punching trim, laminated waste and especially waste containing at least one thin sectioned product, prior metals separating art has encountered difficulty in effecting separation by the usual properties of magnetism, density, and size.
Platelets contained in shredded waste do not respond well to the air flotation and vibratory conveying actions of conventional separation "gravity tables." Platelets may, after cutting, remain flat or may be rumpled, folded, or rolled into tubes or other forms which give no constant and predictable "apparent density" or "apparent specific gravity" which is the property enabling separation to occur on the "gravity table" separators.
Furthermore conventional art can satisfactorily effect certain separations, such as separating shredded waste toothpaste tubes from residual paste, plastic caps and iron closure clips, but such thin walled flake-like product is of very low value because it is so bulky to handle, so poor a heat exchanger that it melts slowly in remelt furnaces and oxidizes to a damaging degree in so doing because of the great surface area exposed to the heat and air. Beer, motor oil, and soft drink cans similarly may be reclaimed from mixed wastes by hand sorting, but also represent high labor cost and low valued products because of similar reasons plus the fact that if they are not shredded and merely baled or briquetted, the contained moisture, residual product, dirt, ink enamel contamination, and foreign metal and non-metal contamination lowers the value even further.
In addition to the above mentioned, other examples of waste having thin walled components are: coaxial cable, heat exchanger tubing consisting of thin walled copper and aluminum and sometimes solder, printed circuit boards and other metal-plastic laminates, assorted electronic circuit assemblies, condensers, transformers, canned relays and condensers, and future mixed metal and plastic laminates currently being tested for solar heating systems.
Prior reclaimed metals separation art, using the dry process, consists essentially of the general steps of: (1) gross manual separation (2) reduction to airveyable size and polishing the discrete particles (3) magnetic separation of iron (this may occur at several locations) (4) particle sizing by grading screens and (5) specific gravity separations.
Separations are based on magnetic removal of iron and on differences of specific gravity or density of whatever shaped particles are being separated. Because particle shapes vary so greatly, we use the terms "apparent density" or "apparent specific gravity." An air blast acts differently on a flat platelet or short piece of fine wire than it does on a denser round sphere. This makes possible the separation of fine wire or platelets or flakes from coarser wire and other denser shapes of the same metal having higher apparent density. Since this is not the goal of the recovery system, it becomes a handicap because the flakes and fine wires of copper may float along with larger but heavier, higher apparent density aluminum particles.
Prior art provided no method for efficiently making separations of all unlike shapes of different materials.